When a radioactive or other hazardous material is handled, or a certain apparatus is manipulated in a hazardous atmosphere containing such material, such a material and/or apparatus must be placed in a shielding box and must be indirectly handled or manipulated from the outside of the box.
As shown in FIG. 1, this shielding box 1 is made of a transparent material for observing the state of things within the box. The shielding box 1 is provided with gloves 3 and bags 4 on its side wall 2, and has an air supply filter 5a and exhaust filters 5b on its lower and upper walls, respectively. The gloves 3 are used for indirectly handling the radioactive material or for manipulating the apparatus by the operator's hands. The bags 4 are employed for removing spent articles from or for inserting necessary articles into the box 1. The air supply filter 5a is used for introducing fresh air into the shielding box 1. One of the exhaust filters 5b is employed for cleaning the polluted air and for discharging the cleaned air out of the box 1, and it is connected to the shielding box 1 at one end thereof and to an exhaust duct 7 at the other end thereof, each such connection being through a connecting pipe 6b having a polyvinyl chloride tube 6a.
FIG. 2 shows a conventional port section for replacing an old glove with a new one which is one of the replacements in the shielding box 1 described above. As shown in FIG. 2, a fixed port 21 having an opening 21a communicated with the outside in its central portion is secured to the side wall 2 of the box 1 through an U-shaped packing 24, by a ring-shaped, plate member 23 adapted to be tightened by a bolt 22. Into the opening 21a of the fixed port 21 is sealingly fitted a port to be replaced or replacement port 25. The fixed port 21 having a threaded portion 26 on its inner periphery is threadingly engaged with a glove replacement port 25 by compressively deforming an elastic screw member 27 adhered to the outer periphery of a larger cylindrical part 25a of the port 25 which will be hereinafter described. The replacement port 25 comprises two cylindrical parts 25a and 25b, the former being larger than the latter in diameter. The larger cylindrical part 25a of the replacement port 25 is provided with a pin 29 on its rear end surface and a hole corresponding to the pin 29 on the front end surface thereof. Over the smaller diameter cylindrical part 25b is tightly mounted a base 3a of the glove 3 by means of sealing band 30 and an O-ring 31. In back of this replacement port 25, another new glove replacement port 25 having the same construction as the former port is standing ready in a situation that a new glove 3 is sealingly fixed to the latter port 25 (the same reference numerals designate an identical part, so that the repeated description thereof is omitted).
In operation of replacing the old glove 3 with a new one, first the old replacement port 25 screwed into the fixed port 21 is brought into contact with the new replacement port 25 having a new glove 3 by inserting the pin 29 into a hole 28 of the latter port 25 for combining the two ports 25. Then, the combined replacement ports 25 are simultaneously pushed forward while subjecting to a rotational torque by an extruder (not shown) arranged behind the new replacement port 25. Therefore, when the new replacement port 25 reaches a predetermined position, the old replacement port 25 is automatically dropped into the shielding box 1, thereby achieving renewal of the port 25, and hence glove 3.
FIGS. 3 and 4 show the constructions in which a replacement bag 4 and a replacement filter 5 are sealingly fixed to the replacement port 25 elastically screwed into the fixed port 21, respectively. In these examples, renewals of the bag 4 and the filter 5 are carried out in a manner similar to that of replacement of the glove as shown in FIG. 2.
The structure of the replacement port section in the shielding box 1 described above is disclosed, for example, in U.S. Pat. No. 4,156,146 and Japanese Patent Disclosure No. 149597/77.
However, according to the structure of the replacement port section of the conventional shielding port 1, for the purpose of renewal of the replacement such as the glove, bag or filter fixed to the replacement port 25, a great rotational torque must be applied to the replacement port 25 by means of a large-sized, complicated extruder because of the very tight engagement of the fixed port 25 with the replacement port 21 through the threaded portion 26 and the elastic screw member 27.
In view of the above-mentioned features, the present invention provides an improved structure of a port section for mounting a replacement on the shielding box. According to this structure, a plurality of elastic rings in a compressively deformed state are arranged between a fixed port and a replacement can be safely carried out only by applying a pushing force to the replacement port in an axial direction thereof, without applying a rotational torque to the port.